Category: Structure

One of the biggest challenges to creating an energy efficient house is to reduce the air leakage as much as possible. While we have chosen to use ICF and SIP framing to greatly reduce the air leakage in the walls, and Nudura Ceiling for ceiling insulation, the gaps and interfaces need to be sealed as well in order to be air tight as possible, and the choice of the casement fiberglass windows.

We chose to spray foam insulate the weak points of the house; the ledger board area where the SIP interfaces to the ICF, the penetrations around the house to the outside, the pot light wire penetrations into the attic, and where the walls on the 2nd floor meet the ceiling.

Before the basement concrete slab was poured, a 2″ thick EPS (R7) was put in place to reduce the heat transfer to the soil beneath. In addition, PEX tubing was run in 90% of the basement floor space to allow for in-floor radiant heating. In-floor radiant heating allows for a more comfortable basement floor as it is no longer cold to walk on, and is efficient as heat rises throughout the house in the winter, as well as a reduction in the heating area that the fan coil has to service. The garage was insulated and roughed-in with the same system for the ability in the future of a heated garage.

The tubes are connected to the Daikin Altherma system, which provides radiant heating to the basement floor as well as the fan coil to heat the ground and second floors, as well as heating the hot water for the house.

The original architectural design called for a combination of stone and stucco for the exterior of the house. But considering the majority of the house was wrapped in ICF and EPS, the most logical choice of material was stucco, as it required an EPS substrate. After we had priced the stone installation, made more difficult with the ICF and EPS as the surface material was not structural, we decided to change the design to an all stucco exterior cladding.

Our choice was to use the Dryvit TAFS (textured acrylic finish system) on the ICF, primarily because of their TerraNeo finish, which gave it a granite look without the cost of stone. Dryvit is one of the leading stucco systems manufacturer in the world, and their TerraNeo finish has chipped granite flakes in the mix to give it a more interesting and pleasing aesthetics for accent areas, a combination that gave it a very unique look, and a glimmer and sheen that can be seen at varying sun angles or on an overcast day.

Our ceiling insulation material is from Nudura, the same manufacturer as our Insulated Concrete Blocks in the exterior walls. The Nudura Ceiling Technology is a 2.5″ or 3.5″ sheets of EPS with built-in wood strappings for simple installation of drywall. These were delivered onsite as 4’x8′ sheets with ship lap edges, which provides a tight fit at the seams.

Our installation consisted of, from top to bottom, the roof truss, a 1/2″ sheet of drywall, a 3.5″ sheet of the Ceiling Technology, followed by another 3.5″ sheet running in perpendicular direction, and finally a finish sheet of 1/2″ sheet of drywall. The ceiling insulation “sandwich” assembly hangs on the underside of the roof truss system, which completely eliminates any thermal bridging of wood.

In total, we have 7″ of EPS, which would in theory only net an R27 based on the EPS alone, and below what the Ontario Building Code requires. However, because of the reduced thermal bridging and the greatly reduced air leakage, Nudura has tested the product in the field and have shown for the product to perform at an equal or greater than an R60 fiberglass batt or loose fill type insulation.

For our project, there was a cost increase of approximately $7,500 compared to a 12″ loose fill sprayed in cellulose, but with far better performance in heat loss as well as air infiltration.

Windows are inherently a weak point in the building envelope in terms of its insulative properties. Wall assemblies, to the Ontario Building Code, requires it to be insulated to R-19. Compared that to windows, the minimum requirements for an Energy Star window is R3.2 for our region (Southern Ontario, Zone B). However, while windows can be a source of heat loss, they can also be a source of heat gain as well, which is bad in the summer, but advanteageous in the winter. Our choice involved a combination of strategies to take a balanced approach to the problem.

We looked at windows from various manufacturers, and compared the R-values of the windows. What we found was that triple pane windows in general offer a higher R-value compared to double panes, but at a price premium. To complicate matters, our design called for large casement windows, which when combined with the weight of the triple pane glass, caused us to look at fiberglass framed windows exclusively.

Fiberglass frames have several benefits. They are far stronger than vinyl frames, and would withstand the test of time much better in our case of triple pane casements, the largest of which would be 30″ wide by 60″ tall. Each of the casements weighed in excess of 100 pounds, and one can imagine the stress of the weight while the window is opened with little support. The other major benefit is that in differing temperature extremes, fiberglass expands and contracts at a rate very similar to glass, while vinyl expands and contracts much differently, giving the potential of an increased air infiltration compared to the ideal test environment of which the standardized testings are based.

When selecting coatings for the windows, we tuned it based on the exposures of the windows. For north, east, and west facing windows where the sun shines rarely on it, we selected windows that offered us the best R-value. For the south facing windows, however, we chose windows that had coatings that allowed for a higher solar gain heat coefficient (SGHC) for heating benefits in the winter, by giving up some R-value for the windows. We countered the effect of the gains in the summer by calculating sun angles and designing the overhangs above the windows to block sun in the summer, but at a lower sun angle in the winter, the sulight would enter the house.

Our Fibertec Windows offered an R-value of 7.7 for the fixed panes, and 5.5 for the operable casements, far exceeding the energy star requirements. The south facing windows offered an R-value of about R4 for the operables, but the SGHC was increased from 0.26 to 0.44 to allow for more heat gain in the winter. Our other reason for selecting Fibertec windows was for their hinge design, as it sat closer to the bottom of the frame for better support of the heavy triple pane casements. Their custom brickmould that are channel locked to the window also allowed for an easy installation that reduced on-site installation time. We estimated a total cost increase of about 25% from a traditional double pane vinyl windows.

CaGBC LEED for Homes – Points can be acheived in Energy and Atmosphere, either via the air leakage tests (EA 3.3) and the exceptional windows (EA 4.3), or exceptional energy performance (EA 1.2) via the ERS/HERS method.

These joists are a premium from an engineered I-joist (which are the standard choice for floor joists), but offers more flexibility in ducting and plumbing design. It also uses less than 1/2 the amount of wood than dimensional lumber, and can be made of wood harvested from a young growth tree.

The main retangular chase is an 8 1/2″ x 21″ opening, which allowed us to fit both the supply and return air trunks through, with the rest of the ducting and piping running through the triangles of the joist. A traditional I-joist would have required significantly more labour to cut openings through the joist, if there were enough space to do so, or limit the trunk and duct runs to be parallel to the joists, or would require bulkheads and frame-outs to hide the ducting.

Open Web Joist - Chase Opening

The joists allowed us to reduce the boxes and bulkhead to hide ducting to almost zero, with the exception of inside a main floor closet and the main floor powder room. It also allowed us to create a basement ceiling with minimal bulkheads, except where load bearing beams are installed.

We estimated an upcharge of about $1.25-$1.50/sq.ft. floor space for an open web design from I-joists. However, we were able to offset this cost by building an 8′ basement height instead of a 9′ basement and still be able to get 8′ clear, as the bulkheads are no longer an issue.

Our joists were engineered, manufactured, and supplied by Kent Trusses of Sundridge, ON. These joists are sold in 2′ increments in length, and the ends of these joists are trimable by up to 1′ on each end, therefore not requiring exact measurements when ordering, and flexibility of install on the job site.

CaGBC LEED for Homes – Points can be acheived in Material and Resources 1.4 for open web floor trusses, and in our case, MR 2.2 for local production.

Part of our exterior wall system were constructed with structured insulated panels (SIP). We used these panels in two areas: in areas where we could not use ICF because of a lack of a supporting wall underneath to bear the weight of the concrete in the ICF, and in wall areas that faced into an unconditioned area, such as the wall separating the garage and the living space, and a section of walls that faced into the lower attic.

Our SIPs are made of two sheets of oriented strand boards (OSB), with expanded polystyrene (EPS, aka Styrofoam) sandwiched in between. Various sizes and thickness are available, and for the majority of the SIPs we used had either 4’x9′ or 4’x10′ sheets that were 8 1/4″ thick in total (7 1/4″ EPS). Channels at the edge are carved out for installation of splines using 2×8 lumber as well as for the plates. Every 4′ a spline was installed, and glued and nailed together to the OSB. In our case, we had ordered the panels with built-in channels for electrical wiring. What surprised us was how rigid the wall system as we were installing even without the nails in place; the tight fit of the spline to the OSB and the rigidness of the SIP allowed it to stand on the base plate with no flex whatsoever.

Benefits include an air tight structure, and reduced thermal bridging compared to traditional timber frame, as “studs” are every 48″ instead of every 16″. The fit between the OSB and the spline/plates are also very tight and glued together to minimize potential air leakages.

In costs, we estimated this to be about a $3/sq.ft. wall space upcharge for material and labour from traditional timber framing, and about $6/sq.ft. less than the ICF.

Our SIPs are from Insulspan, sourced through Kent Trusses (who also supplied our floor and roof trusses). The SIPs were ordered in 6 1/2″ and 8 1/4″ thicknesses, in 4’x9′ and 4’x10′ sheets, with wiring channels put in at 14″ and 44″ from floor.

CaGBC LEED for Homes – Points can be achieved in Energy and Atmosphere, either via the air leakage tests (EA 3.3) or exceptional energy performance (EA 1.2) via the ERS/HERS method. Points is also available in Material and Resources (MR 1.4) for SIP and MR 2.2 for local content.

For our house, we have chosen to use insulated concrete forms (ICF) as the primary wall system for the exterior walls of the house, with sections that are structural insulated panels (SIP).

ICFs are made of 2 sheets of expanded polystyrene (EPS, aka Styrofoam) with concrete poured in between. The materials comes in blocks, and is assembled on-site in a similar fashion to Lego blocks. The blocks act as the form work for the concrete as it is poured into the cavities between the two sheets of EPS, and is a stay-in-place form work, as the blocks of EPS are not removed after the curing of the concrete. The EPS acts as the insulation for the wall, and the concrete provides the strength, and a total air and thermal break between the inside and outside of the walls.

On the inside, drywall is directly fastened to the ICF, as the ICF have built-in plastic strappings that act both as a structural component for strength and for holding the EPS together, as well as for screwing the drywall into the straps. For electrical, the EPS is thick enough to accomodate the mounting of the electrical boxes, with the wires being embedded into the EPS. No penetrations through the concrete is required, except for venting purposes.

This method of building provides a much stronger structure, which may be an advantage if you are in an natural disaster prone area. Other benefits include a much tighter building envelope, as the concrete wall system is a monolithic system and no possible penetrations for air leakage. This translates into a significant reduction of heat loss, as up to 1/2 of the heat loss of a house can be attributed to air leakage. If you live near a noisy environment, another benefit is the significant noise reduction from the outside.

In using the ICF, we decided to go from basement to the roof, except in areas on the second floor where there was nothing underneath to bear the weight of the concrete. For the basement walls, this is fairly cost competitive with traditional poured concrete walls or cement blocks. Once we went above ground, however, it becomes a significant cost upgrade to use ICF. For this reason, there are some builders that will choose to use ICF for the basement, and either traditional timber frame (cheapest) or SIPs (more expensive than traditional, less expensive than ICF) for above grade exterior walls. Expect an upcharge of $8-10/sq.ft. wall space material and labour from traditional timber frame, and an upcharge of $5-7/sq.ft. wall space from SIP, depending on complexity of project.

In our house, we have chosen to use blocks manufacturered by Nudura, supplied through our contractor for the exterior “framing” (Stevens Construction). The blocks consists of 2 5/8″ sheets of EPS on the outsides, with a 6″ cavity for the concrete. Other cavity thicknesses are available, starting at 4″ and increasing in 2″ increments.

CaGBC LEED for Homes – Points can be acheived in Energy and Atmosphere, either via the air leakage tests (EA 3.3) or exceptional energy performance (EA 1.2) via the ERS/HERS method. In our case, it would qualify for Material and Resources (MR 2.2) for local content, as the concrete and the ICF are both manufactured within 800km.